The invention relates to a printed circuit board. Further, the invention relates to a method for producing a printed circuit board and a testing device for testing a printed circuit board.
A printed circuit board is already known in practice. Printed circuit boards of this known kind are populated with electrical and electronic components which form a circuit of an engine control unit, for example. In the manufacturing process of the printed circuit board and after populating the printed circuit board with the electrical and electronic components, the function of the printed circuit board or of the circuit must be tested in order to be able to exclude incorrect population or component defects. In practice, this is carried out by means of pin-shaped testing heads, which make electrical contact with the printed circuit board in the region of test zones in order to thereby be able to test resistances, for example, between certain points of the circuit or similar. These test zones are formed by areas of the printed circuit tracks in which, in contrast to other areas of the printed circuit tracks which are only used to carry current, no protective layer in the form of a solder resist varnish has previously been applied to the printed circuit track. Furthermore, the test zone is provided with a solder layer in order to guarantee that the test zone makes good electrical contact with a mentioned pin-shaped testing head.
With the printed circuit boards known in practice, no solder resist varnish is applied over the whole width of the printed circuit track in the region of the test zone. Further, the solder layer covers the whole width of the test zone. A problem here is that the solder layer can penetrate a region outside the printed circuit track. This is particularly problematic when, due to the usually close spacing of the printed circuit tracks, the solder layer cannot be prevented from finding its way into the region of a printed circuit track adjacent to the test zone so that electrical short circuits can occur. In particular, the trend towards ever smaller distances between the printed circuit tracks, which are necessary in order to achieve higher circuit densities, therefore requires much closer tolerances with regard to the application of the solder layer as well as stricter quality checks for checking that there are no short circuits to the printed circuit tracks adjacent to the test zone, both measures which burden the production of a printed circuit board with additional costs.